Crack propagation behavior in rubber materials

Within the linear viscoelastic theory, crack tip fields are calculated at various crack tip velocities. A transition from rubbery to glassy material behavior in the vicinity of the crack tip can be observed. Shear and bulk behavior is analyzed separately. Whereas the increase of tearing energy at higher crack tip velocities can be ascribed to the shear behavior, bulk behavior influences the fracture mechanism. The results support experimental investigations that the instability separating stable from unstable crack propagation is related to a change in the fracture mechanism. At low crack tip velocities, material separation is the result of formation, growth, and coalescence of cavities. At high crack tip velocities, cavitation is suppressed and fracture is driven by a rather brittle mechanism resulting in a decreased amount of energy to propagate the fracture process zone. Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 5, pp. 882–891. This article was submitted by the authors in English.     

Determination of inorganic constituents and polymers in metallized plastic materials

This work presents results obtained in the analyses of metallized plastics by neutron activation analysis (NAA) and results of polymer identification by infrared spectroscopy (IR) and differential scanning calorimetry (DSC). Metallized plastics of packagings, automobile accessories, toys, house wares, cards and compact discs were selected for these analyses. Toxic elements such as As, Cd, Cr, Ni, Sb and Sn as well as Ba, Br, Ca, Co, Fe, Sc, Se, and Zn were determined and their concentrations presented great variability. IR and DSC assays indicated that polyethylene, polypropylene, poly(ethylene terephthalate), polycarbonate, acrylonitrile-butadiene-styrene terpolymer are main types of polymers used in metallized plastics.     

塑料食品接触材料中32种添加剂的快速筛查EI北大核心CSCD

A rapid screening and quantitative analysis method for 32 additives including antioxidants, UV absorbers,phthalates and adipate plasticizers in polycarbonate （PC）, acrylonitrile butadiene styrene （ABS） and polyvinyl chloride （PVC） food contact materials was established by pyrolyse-gas chromatography-mass spectrometry. After shearing, the samples were directly injected into the pyrolyzer, 32 additives were resolved from the food contact materials by thermal cracking at 310 ℃ , then qualitative and quantitative analysis were carried out by gas chromatography-mass spectrometry. The results showed that within certain concentration ranges, 32 target compounds had good linear relationships with the correlation coefficients of r≥0.997, and the detection limits were 4.1-21.1 mg/kg. The recoveries of the method ranged from 78.4% to 97.7%, with the relative standard deviations （RSDs） of 2.7%-15%. The method is suitable for rapid screening of 32 additives in plastic food contact materials. © 2023 the authors.     

On the mechanisms of initiation and propagation of plastic instability in polyethylene under tensile drawing

The development of a plastic instability in a high-density ethylene-butene copolymer under tensile drawing was monitored by means of a video-controlled optical extensometer in order to study the mechanism of initiation and propagation of necking. True-stress true-strain curves measured along the neck at various times of the drawing are compared with the curve recorded as a function of time at the locus where the neck started. A strain rate gradient is shown to build up during the stage of neck initiation. Evidence is given of tensile normal stress in the concave part of the neck shoulder. X-ray diffraction reveals an oblique preferred orientation of the crystal c-axis that is governed by the lower energy-consuming pathway for the deformation. This is responsible for the plastic flow localization owing to an improved shear ability. The gradual c-axis orientation towards the draw direction as the neck grows involves a strain-hardening effect that leads to neck stabilization. The conclusion is put forward that neck propagation lies in the gradation of the preferred orientation along the neck shoulder rather than in stress triaxiality. Comparison with a parent low-density copolymer shows a better trend for oblique preferred orientation of the c-axis and a reduced propensity for localized plastic flow thanks to a more homogeneous distribution of the stress over the crystallites. © 1996 John Wiley & Sons, Inc.     

Radon exhalation rate in building materials using plastic track detectors

The radon flux emitted from building material samples and from the surface of building materials could be determined using a simple and reliable method. This method was based on the use of cellulose nitrate films (LR-115 II). The samples and the detectors were placed in a closed can of known dimensions. Tracks due to alpha-particles of radon that migrate from the building material into the air space in the chamber were registered on the LR-115 film. The detectors were chemically etched in 2.5N NaOH solution at 60±1 °C for 115 minutes. Exhalation rates of various building material samples and of building surfaces of various building components were determined. The results obtained by this technique could be used to establish a database for average radon exhalation rates for all available building materials and walls or floors.     

The autofluorescence of plastic materials and chips measured under laser irradiation

Plastic materials have the potential to substitute for glass substrates used in microfluidic and microTAS systems adding flexibility in materials' choices. Optical quality plastic materials with a low autofluorescence are crucial for optimal detection by fluorescence and laser induced fluorescence techniques. This paper summarizes a series of optical investigations on commercially available plastic chip materials (PMMA, COC, PC, PDMS) and chips made from those materials. Intrinsic optical constants of plastic materials-refractive index for bulk materials-determined by spectroscopic ellipsometry and transmission spectroscopy in the visible range are presented. The laser-induced autofluorescence of materials and chips was assessed at four laser wavelengths, namely, 403, 488, 532 and 633 nm. Considerable bleaching of the autofluorescence was observed under continuous laser illumination. Overall, the longer wavelength laser excitation sources yielded less autofluorescence. PDMS exhibited the least autofluorescence and was comparable to BoroFloat glass. In all cases, chips exhibited slightly higher autofluorescence than the raw plastic materials from which they had been made.     

Evaluation of plastic packaging materials used in radiation sterilized medical products and food

This paper studied the results of evaluation on resistance to radiation, moisture permeability, bacteria permeability, tensile strength, elongation at break and sealing ability for several plastic films available on the market. The result shows that nylon, sarin, and polyethylene complex films, high and low density polyethylene films are applicable for packing of radiation sterilized products.     

Electrode materials derived from plastic wastes and other industrial wastes for supercapacitors

The present review not only devotes on the environmental consequences of plastic bag wastes and other industrial wastes observable in the landfills,in the oceans or elsewhere but also gives a new insight idea on conversion of them into worth material,carbon,for the best electrochemical supercapacitor.Transformation of plastic wastes into high-value materials is the incentive for plastic recycling,end-oflife handling case for plastic bag wastes in practice quite limited.The plastic recycling waste for reuse saves energy compared with manufacturing virgin materials.Herein,we identified several synthetic methods to convert plastic waste and other industrial wastes into carbon material for supercapacitor.Different kinds of carbon materials,including nanofiber,nanotube,graphene,mesoporous carbon,etc.,have been derived from plastic waste,and thus give a superior potential for transforming trash into a "gold capacitor".Finally,conclusions and future trends of high-voltage supercapacitors were made as well as the easy and mass production of high-performance electrode materials for supercapacitors.Our work offers a promising sustainable approach to handle plastic bags,waste,and other industrial wastes and provides a new avenue in supercapacitor applications and other areas.     

Natural superabsorbent plastic materials based on a functionalized soy protein

A natural superabsorbent polymer (SAP) material based on an acylated soy protein was studied as a green alternative to non-biodegradable SAP. In order to obtain the natural SAPs, different amounts of succinic anhydride were used as acylating agent. Once the functionalized protein was obtained, it was mixed thoroughly with glycerol and then molded through a lab-scale injection molding device. Water uptake of samples obtained reached values much higher than those based on unacylated protein. Moreover, a greater extent of the acylation reaction led to higher water uptake values for the corresponding SAPs, probably related to their higher hydrophilic character. Water imbibing capacity measurements and thermogravimetrical analysis (TGA) seemed to confirm this. The presence of larger porous regions in acylated samples observed in SEM images could also play a role in their higher water uptake values.Furthermore, an increase in the extent of acylation reaction led to plastics with lower Young's modulus and higher extensibility.     

Mechanics of peeling of rubbery materials. II. Initiation and propagation of peeling

The peel strength of a joint with flexible materials bonded by an elastic adhesive was evaluated in relation to the fracture mechanism. It was found that initiation and propagation of peeling are governed by different mechanisms. Initiation (the formation of an initial crack) occurs when the maximum stress in the adhesive layer reaches a definite value. In this case, the strength f_i in a trousers-type peeling is given by 2f_i = y₀σ_b?_b, where y₀ is the half-thickness of the adhesive layer, σ_b is the tensile strength, and ?_b is the tensile elongation of the adhesive. On the other hand, propagation is governed by the surface energy of the adhesive. In this case, the peeling strength f_s is determined by a balance of energies. For trousers-type peeling it is given by 2f_s = Γ, where Γ is twice the surface energy. These results were verified experimentally.     

Conducting polymer-based array for the discrimination of odours from trim plastic materials used in automobiles

This paper reports the test of the use of an electronic nose based on chemoresistive polymeric sensors for the discrimination of eight sample materials used in the car manufacture, including parts fabricated in polyurethane (PU). Principal component analysis (PCA) and cluster analysis (CA) have been used in order to classify and identify the odours coming from the parts under study. Good separation among odours of samples of comparable composition has been obtained using the first coefficients of the fast Fourier transform (FFT) of the whole curve as the input variable of PCA. These results show the feasibility of the conducting polymer array of sensors to discriminate odours for the air cabin quality control.     

超高效合相色谱法快速检测塑料食品接触材料中13种紫外吸收剂

建立了一种同时检测塑料食品接触材料中13种紫外吸收剂的超高效合相色谱法。以甲醇为溶剂对塑料食品接触材料样品进行超声提取，经C18固相萃取柱净化，过0.22 μm有机滤膜，采用超高效合相色谱仪分析。选择ACQUTY UPC² HSS C18 SB色谱柱（150 mm×3.0 mm，1.8 μm），以超临界二氧化碳为流动相，异丙醇为改性剂进行梯度洗脱，在最优色谱条件下，13种紫外吸收剂能够在4 min内实现有效分离。结果表明，在各自线性范围内，13种紫外吸收剂的线性关系良好，标准曲线相关系数不低于0.9985，检出限（S/N=3）为0.05~0.15 mg/kg，加标回收率为86.8%~115.7%，相对标准偏差为0.73%~5.61%。该方法快速简便，准确可靠，同时大大减少了有机溶剂的消耗，可用于塑料食品接触材料中13种紫外吸收剂的快速检测。     

高效液相色谱-串联质谱法测定焙烤食品及其塑料包装中31种邻苯二甲酸酯

建立了高效液相色谱-三重四极杆串联质谱（HPLC-MS/MS）测定焙烤食品及其塑料包装中31种邻苯二甲酸酯（PAEs）的方法。焙烤食品采用乙酸乙酯超声提取,提取液经冷冻（-18℃）、低温高速离心净化,剪碎后的塑料包装材料采用体积比为1：1：1的甲醇-丙酮-正己烷混合溶剂进行液液超声萃取后进入HPLC-MS/MS分析。采用MGⅢC₁₈色谱柱（2.0 mm×100 mm,5 μm）,选择反应监测（SRM）模式测定。实验结果表明,31种邻苯二甲酸酯的特征离子质量色谱峰的峰面积与其质量浓度在各自的质量浓度范围内线性关系良好（r²≥0.9958）。样品加标回收率除邻苯二甲酸二月桂酯（DLP）为70.9%～109.7%外,其余30种化合物为80.1%～113.0%,相对标准偏差（n=6）为1.0%～13.7%。31种PAEs的检出限在0.02～8.15 μg/kg之间,定量限在0.07～27.17 μg/kg之间。应用该方法检测了面包、饼干、糕点、馅料4大类焙烤食品及其塑料包装中31种邻苯二甲酸酯的含量。该方法具有操作简单、快速、准确度和精密度高等优点,满足日常检测的要求。     

高效液相色谱法同时测定塑料和纸质包装材料中6种荧光增白剂

建立了同时测定塑料和纸质食品包装材料中6种脂溶性荧光增白剂(FWA 135、FWA 184、FWA 185、FWA199、FWA 378和FWA 393)的高效液相色谱方法。用三氯甲烷-乙腈(3∶7,v/v)混合溶液提取,经HLB小柱净化后用高效液相色谱-荧光检测法进行定性定量分析。采用Phenomenex C18色谱柱分离,以5 mmol/L的乙酸铵水溶液和乙腈为流动相,进行梯度洗脱。结果显示:FWA 393在15~1500μg/L范围内的线性关系良好,其余5种荧光增白剂在5~500μg/L范围内线性关系良好,相关系数均大于0.999;加标回收率为80.4%~125.0%;相对标准偏差(RSD,n=6)为1%~13%。应用该方法分析了市场销售的12个样品以验证方法的实用性。该方法前处理简单,回收率高,精密度好,适用于食品包装材料中6种荧光增白剂的检测。     

Understanding the interfacial region in organic ionic plastic crystal composite electrolyte materials by solid-state NMR

Organic ionic plastic crystal composites exhibit properties that make them suitable for many applications including energy storage devices and CO₂ separation. In most cases, the mixing of organic ionic plastic crystals with a polymer, salt or a porous material leads to the formation of interfacial regions that can enhance the ion transport of desired ions like Li⁺ for battery applications. The study of these interfacial regions is challenging and requires the use of spectroscopic techniques like solid-state NMR to characterise the structure, interactions, and ion dynamics. This article summarises the advantages and challenges of organic ionic plastic crystals and their composites, and the common NMR methods used to study the interfacial regions between their components.     

Contribution of size exclusion chromatography and thermal analysis methods in the study of the radiochemical behavior of plastic materials

Sterilization by irradiation techniques is considered to be an improved method to treat polluted products of human consumption. Secondary effects, that may be generated in the components of packaging materials, could induce organoleptic damage and some physico-chemical modifications, observed especially in plastic materials. In order to demonstrate any such secondary changes, we have investigated the effects of beta-irradiation (a treatment which could induce either a reticulation or a cleavage in a polymeric sequence) on three polymers; namely, low density polyethylene, polystyrene and polyvinyl chloride. The techniques used to identify irradiation-induced modifications of these polymers were size exclusion chromatography and thermal analysis. Thermal analysis showed a decrease in the percentage of crystallinity of polyethylene after its radiosterilization. Exclusion chromatography highlighted a reticulation for irradiated polyvinyl chloride and polystyrene.     

Bibliometric analysis and an overview of the application of the non-precious materials for pyrolysis reaction of plastic waste

Huge plastic consumption and depletion of fossil fuels are at the top of the world's environmental and energy challenges. The scientific community has tackled these issues through different approaches. Catalytic pyrolysis of plastic wastes to valuable products has been proved as a sustainable route which fits with the circular economy aspects. The design of catalytic materials is the central factor for performing the catalytic conversion of plastic wastes. This review aims to conduct a Bibliometric analysis of the pyrolysis of plastic wastes and non-precious-based catalysts by mapping research studies over the last fifty years. The analysis was developed via VOSviewer and RStudio tools. It showed the historical progress regarding plastic waste pyrolysis to produce valuable products and chemicals worldwide. The research shows that the top five countries with the highest citations and publications in this field were Spain, China, England, the USA and India. The Journal of Analytical and Applied Pyrolysis had the most comprehensive coverage of plastic waste. The relationship between the catalyst and the mechanism of plastic waste can influence the production yield and selectivity. The research gap and underrepresented research topics were identified, and previous research studies on developing non-precious-based catalysts that were most relevant to the current topic were reviewed and discussed. The challenges and perspectives on catalyst preparation and development for material complexity were critically discussed. Challenges of previous studies and directions for future research were provided. This report might guide the reader to take a general look at plastic waste valorization by pyrolysis and easily understand the main challenges.     

激光烧蚀-电感耦合等离子体质谱法测定塑料中的Pb、Cd、Cr和Hg

采用激光烧蚀固体进样技术的电感耦合等离子体质谱法(LA-ICP-MS)测定了塑料中的Pb、Cd、Cr和Hg。选择了线扫描激光烧蚀方式,并从灵敏度和稳定性角度优化了工作参数。根据计算分馏因子考察了分馏效应,结果表明,所测元素分馏效应小。塑料中Hg的记忆效应严重,认为主要来自样品表面吸附,减小样品的表面积可减小Hg的记忆效应。以聚丙烯标准物质及其空白片作校准曲线,应用于ABS、PPS、PA66+30%GF、PVC、PTFE等实际塑料样品的测定,测定结果与ICP-OES(XRF)法测定值基本吻合。Pb、Cd、Cr和Hg的检测下限分别为0.002、0.001、0.08和1.5 mg/kg。